How to cut metal with a plasma cutter

(Last modified: March 21st, 2019)

Plasma cutting was discovered in the 1960’s when welders tried to turn the gas up on their arc welders to improve speed and productivity; what they discovered was that once you reach a certain intensity, the equipment no longer joins metal, but cuts it. Plasma cutters work by combining an electric charge with compressed air being discharged at the tip of the cutting torch- the arc ‘super- heats’ the compressed air to form ‘plasma’.

metals4U plasma cutting

Tips for cutting metal with a plasma cutter.

  • Ensure you have a suitable workspace for using this cutting equipment, this includes a stable workbench and all your PPE to hand; plasma cutters function at around 45000°F / 25000°C, so regular Tig and Mig gloves will not be adequate. We recommend these  Skintex welders’ gloves to offer superior protection when working with plasma cutting equipment.
  • Ensure the plasma cutter is switched off and plug it into the power supply ready to start. Check that cables and hoses are in good condition and not crossing over or caught on the metal you are intending to cut.
  • Attach the air compressor hose to the plasma cutter- make sure the connection is secure then turn on the air to the correct pressure-too high will blow out the plasma, too little will not enable a cut to be made. This will typically be between 60-65 psi.
  • Ensure there is at least one water trap filter/ disposable air filter in the hose to maintain a dry air supply to the arc; this will prevent splutter or maybe worse- water and electricity are best avoided being mixed during any operation.
  • Place the metal to be cut on a bench or cutting table and secure the ‘Earth Clamp’ on the metal, close to where the cut will be.
  • Switch the plasma cutter on and adjust the current to the desired setting.

General guidance for amperage suggests 20amps will be enough for a 3mm deep cut, after this, the amperage can be increased by 10 amps per additional 3mm of cut depth.

Thickness of metal in mm Suggested amps
3 20
6 30
9 40
12 50

 

  • Put on your PPE.
  • You are now ready to cut the metal- the standard technique for plasma cutting is to ‘drag’ the cutting tip across the metal. Hold the tip at a 45° angle facing away from you and drag the cutting tip towards you; this will blow sparks away from you- but stay vigilant, the sparks will still fly around randomly at times. Once cutting has begun the torch is best held perpendicular to the metal being cut; if sparks travel backwards, simply adjust the angle of the torch to face away again.
  • Regular checks of the cutting tip, nozzle, and electrode for signs of damage and wear will help protect against unpredictable and erratic cutting and machine performance. Be careful to not touch the plasma cutter to the metal as this may fuse the cutting tip to the metal and may cause the cutter to go out; using ‘drag cups’ or a ‘drag shield’ can keep the tip from coming into direct contact with the metal. If no drag shields are available, try to maintain a 6mm gap between the metal and the cutting tip.
  • Once the cut has been completed, turn off the machine and disconnect the ‘earth clamp’ and then turn off the air. While tidying up the cables and hoses it is a good opportunity to carefully check them and replace anything that show signs of excessive wear or damage.